In production of an olefin compound, a rearrangement reaction of a double bond can occur during a production process or after production to yield a structural isomer which has the same molecular formula but an unsaturated bond at a different position. If the structural isomer has the reactivity comparable to that of the intended olefin compound, there will arise such a problem that it changes the properties of the olefin compound. On the other hand, if the reactivity of the structural isomer is low, there will arise another problem that it interferes with the reaction of the intended olefin.
There is still another problem that the structural isomer has a boiling point too close to that of the intended olefin to separate it by distillation. Furthermore, there was still another problem that even if an attempt to separate them was made by means of azeotropic distillation, extractive distillation or chromatography available for separation of compounds having boiling points close to each other, the properties of the structural isomer (e.g., polarity and the like) were so similar to those of the intended olefin that it was difficult to separate them from each other.
Under these circumstances, the following methods have been proposed to produce only the intended olefin, while producing a structural isomer as little as possible.
(a) A method wherein a compound represented by the following formula (A1-2) is obtained by vapor-phase pyrolysis of a compound represented by the following formula (A1-1), and then a dechlorination reaction is conducted in the presence of zinc to form a 3-butenyl group, thereby obtaining 3-butenyl vinyl ether represented by the following formula (A) (JP-A-1-143843).FC(O)CF(CF3)OCF2CF2CFClCF2Cl  (A1-1)CF2═CFOCF2CF2CFClCF2Cl  (A1-2)CF2═CFOCF2CF2CF═CF2  (A)
(b) A method wherein a compound represented by the following formula (A2-2a) is produced by pyrolysis of a compound represented by the following formula (A2-1) as a starting material, and then a dechlorination reaction of the compound is conducted, thereby obtaining 3-butenyl vinyl ether represented by the following formula (A) (JP-A-2-311438).CF2ClCFClOCF2CF2CF2CF2COF  (A2-1)CF2ClCFClOCF2CF2CF═CF2  (A2-2a)CF2═CFOCF2CF2CF═CF2  (A)CF2ClCFClOCF2CF═CFCF3  (A2-2b)CF2═CFOCF2CF═CFCF3  (A-3)
However, multiple steps were required for synthesis of the compound represented by the formula (A1-1) used in the method (a). Furthermore, there was a problem that the production of the compound needed to use reagents difficult to handle, such as fuming sulfuric acid, iodine monochloride, and so on.
Furthermore, the method (b) was proved to have a problem that a rearrangement reaction of a double bond took place in a 3-butenyl group having a fluorine atom at the 1-position, in the compound represented by the formula (A2-2a), thereby producing a thermodynamically stabler compound represented by the formula (A2-2b). If the dechlorination is conducted in the presence of the compound of the formula (A2-2b), there will arise a problem that a compound represented by the formula (A-3) is mixed into the final product.
Here, the compound represented by the formula (A2-2a) has much the same properties, including the boiling point and others, as the compound represented by the formula (A2-2b), and the compound represented by the formula (A) also has much the same properties, including the boiling point and others, as the compound represented by the formula (A-3). Therefore, there was a problem that it was difficult to separate these compounds and it was infeasible to obtain the compound represented by the formula (A) in high purity.
The compound represented by the formula (A), produced by these methods, is useful as a raw-monomer for a fluorocarbon resin. However, in a case where the compound represented by the formula (A) was polymerized in the presence of the compound represented by the formula (A-3), there was a problem that the polymerization was significantly hindered, so as to result in failure in production of a fluorocarbon polymer having a high molecular weight.
On the other hand, the Claisen rearrangement reaction itself is a known reaction. As examples of the Claisen rearrangement reaction in a fluorine-containing compound, there have been reported examples in compounds such as CF2═CFOCH2CH═CH2, CF3 (CF3) C═CFOCH2CH═CH2, Cl2C═CFOCH2CH═CH2, ClFC═CFOCH2CH═CH2 and H(CF3)C═CH(CF3)═CH2CH═CH2 (J. Fluorine Chemistry, 1992, 56, 165), examples of CH2═CH(CF3)OCH2CH═CH2 and CH2═CHOCH(CF3)CH═CH2 (J. Org. Chem., 1990, 55, 1813), an example of the Claisen rearrangement reaction from CF2═CFCF2OCF═CF2 to CF2═CFCF2CF2CF═O (JP-A-2-42038), and so on.
However, none of these documents reported about the Claisen rearrangement in a compound having a 2-butenyl skeleton with a fluorine atom bonded at the 4-position. A document describing such an example is one wherein CH2═CHOCH2CH═CHCF2PO(OCH2CH3)2 with a group containing a phosphorus atom at the 4-position is converted to CH2═CHCH(CF2PO(OCH2CH3)2)CH2CH═O by heating at 140° C. (Chem. Commun., 2000, 1691). However, the reaction was conducted under the same conditions with the compound represented by the formula (2) of the present invention, which contained no phosphorus atom, and found that the Claisen rearrangement reaction did not proceed at all.